1. Field of the Invention
This invention relates to devices for withdrawing fluids from and/or introducing fluids into a cavity or vessel of the body and is more particularly concerned with improvements in multi-lumen catheters and with methods for their fabrication.
2. Description of the Prior Art
Double lumen catheters, also known as double current catheters, are well-known in the art and are widely used in medical procedures such as hemodialysis and the like. In such procedures fluid is introduced through one of the lumens into a vein or other vessel while a corresponding amount of fluid is withdrawn through the other lumen. Typical of double lumen catheters currently available are those described by Mahurkar in U.S. Pat. Nos. 4,568,329; 4,583,968; and 4,692,141 as well as U.S. Pat. No. Des. 272,651. The '329 patent describes a catheter comprising an elongated tube divided into two lumens having semi-circular cross-sections by an integral septum which extends throughout the length of the tube. At the distal end of the catheter one of the lumens opens through a bevelled aperture. The other lumen extends into a second cylindrical portion of enlarged diameter in the transverse direction normal to the plane of the septum, which portion terminates in a conical tapered tip. The '141 patent is based on a continuation of the '329 patent and describes a variation of the structure of the above second portion of the catheter. The Des. Patent shows a similar tip except that the second cylindrical portion does not have the enlarged diameter described in the '329 and '141 patents.
The '968 patent describes a double lumen catheter having a different tip portion. The two lumens are of semi-circular cross-section as before and extend throughout the length of catheter. The distal end of the catheter has a smooth conical tip which merges smoothly with the exterior surface of the tube. One of the lumens extends into and through the tip portion and terminates in an opening in the apex of the tip. The other lumen terminates in an opening in its sidewall at a location which is axially displaced from the conical tip. The remainder of this other lumen, which would otherwise extend into the tip, is blocked off by solid material. This latter feature is said to provide rigidity so that the tip functions as an effective dilator for soft tissue and veins.
The present invention is directed to three-lumen catheters which possess a number of advantages over two-lumen catheters.